ELECTRON SELF-EXCHANGE DYNAMICS OF AN IRON BIPYRIDINE COMPLEX REDOX POLYETHER HYBRID IN ITS ROOM-TEMPERATURE MELT

The derivatization of metal-tris(2,2'-bipyridine) complexes with oligo (ethylene glycol) tails produces ionically-conductive room-temperature melts in which appreciable concentrations of lithium electrolytes dis solve. Charge transport rates in these redox polyether hybrids, in the undiluted state, have been investigated using microelectrode solid st ate voltammetry. In the ligand bpy(CO(2)MPEG350)(2), MPEG350 is -(CH2C H2O)(7)CH3. The apparent diffusion coefficient, D-APP, for the oxidati on of [Fe(bpy(CO(2)MPEG350)(2))(3)](ClO4)(2) is Ca. 10(3) larger than that for [Co(bpy(CO(2)MPEG350](2))(3)](ClO4)(2). This difference is as cribed to transport dominated in the former by electron self-exchange reactions between adjacent Fe(II) and Fe(III) complexes. The very slow physical self-diffusivity in these metal complex melts, measured by t he Co(III/II) reaction, provides an opportunity to assess the effect o f electron donor/acceptor concentration on electron self-exchange dyna mics in a semisolid matrix. Various models have been described for the site concentration dependency of charge transport in redox polymers, including ion association, electron migration, and percolation. This s tudy examines the effects of changing redox site concentration on D-AP P by diluting [Fe(bpy(CO2MPEG350)(2))(3)] (ClO4)(2) isostructurally wi th the analogous Co and Ni complexes, and interprets the results in th e context of the previous models.